The present invention relates generally to oilfield operations, and more particularly, to methods and systems for material transfer.
Oilfield operations are conducted in a variety of different locations and may involve a variety of equipment. The requisite materials for the different operations are often hauled to and stored at a well site where the operations are to be performed. After delivery to the well site, some materials may be transferred to storage units. Much time and expense may be incurred by transferring materials to storage units at the well site.
In hydraulic fracturing operations, for example, proppant may be transferred to a horizontal storage unit, sometimes referred to as a “mountain mover” in the oilfield services industry. A horizontal storage unit may be positioned on a well site pad while the unit is empty. The horizontal storage unit may then be filled, via tractor-trailer proppant transport vehicles, for example. These transport vehicles may have a pneumatic conveying system to facilitate unloading a load of proppant at a particular rate. That rate may be limited by, among other things, the characteristics of proppant; proppant may include, for example, sand or other man-made granular materials and may not convey well in the vertical direction.
By way of example, a typical transport vehicle may unload 40,000 lbs (pounds) of proppant in approximately 30 minutes at an average of approximately 15 cf (cubic feet) per minute, while vertically elevating the proppant stream approximate 13 ft (feet). Additional time—approximately 15 minutes, for example—initially may be required to position and prepare the transport vehicle for unloading. The time required to disconnect the transport vehicle and drive away may add another 15 minutes. Thus, the entire proppant fill cycle may well extend to approximately 1 hour per 400 cf of proppant.
Moreover, there may not be sufficient space at the well site for multiple proppant transport vehicles to unload simultaneously. Thus, to fill a 2,300-cf storage bin may require 6 fill cycles and 6 hours with only one unit unloading at a time. As transport vehicles arrive at the well site, each may have to wait to unload in turn, and transport businesses may typically charge substantial stand-by fees for such waiting periods.
In the alternative, proppant may be transferred to a vertical storage unit. Filling a vertical storage unit may necessitate a conveying system to elevate the proppant vertically. Considering a 30-ft vertical elevation for a vertical storage unit instead of a 13-ft elevation discussed in the prior horizontal storage unit example, the discharge rate may be further limited to approximately 5 to 10 cf per minute. Hence, even if two transport vehicles unload simultaneously, the aggregate unloading rate may nonetheless be significantly lower than the unloading rate of approximately 15 cf per minute in the case of a horizontal storage unit. Expenses and inefficiencies resulting from limitations such those in the examples above are undesirable.
While embodiments of this disclosure have been depicted and described and are defined by reference to exemplary embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.